Niemax K., M. Movre, and G. Pichler, Journal Of Physics B: Atomic And Molecular Physics 12, 3503-3509 (1979).
Pendrill L.R., and K. Niemax, Journal Of Physics B: Atomic And Molecular Physics 15, L147 - L151 (1982).
Niemax K., and L.R. Pendrill, Journal Of Physics B: Atomic And Molecular Physics 13, L461 - L465 (1980).